Spider Fangs Make Perfect Injection Needles

Tarantulas inspire fear enough to create whole movie enterprises on their creepiness, but in reality they're the gentle giant of arachnid-kind.
Published today in the online journal "ZooKeys," Dr. Rogério Bertani has discovered nine new species of the tarantula in the states of Central and Eastern Brazil. The new species are arboreal tarantula, which means they mostly live in the trees, and though they are commonly found in the Amazon rainforest this is not the case with these spiders. Some even live in the houses of people in the region. Of the nine, "four are the smallest arboreal species ever recorded," read the journal's press release.
"Instead of the seven species formerly known in the region, we now have sixteen", said Dr Bertani in the same release. Aside from the nine new species, he rediscovered a thought-to-be-extinct species as well. The discovery of these new species outside of the rainforests indicates the shortcomings of some of the scientific exploration of human populated regions. Even with humanity bearing down on their habitat, new populations could be living right under their feet.
Take a gander at all the eight-legged, hairy beauty of these new species of arboreal tarantula.
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Typhochlaena paschoali preserved female, Camacam, state of Bahia . 40–43 immatures in progression 44 female 45 male, all from E.E. Murici, Murici, state of Alagoas. Photos: R. Bertani.

R. Bertani

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Typhochlaena amma: female, found in city of Santa Teresa, state of Espirito Santo.
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R. Bertani

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Typhochlaena costae: female, found in city of Palmas, state of Tocantins.
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R. Bertani

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Typhochlena curumim: female, found in city of Areia, state of Paraiba.
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R. Bertani

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Pachistopelma bromelicola: male, from city of Jeremoabo, state of Bahia.
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The toothy barbs of a large wandering spider are curved in order to hold the spider's prey in place, and their conical shape helps them resist deformation. Understanding the biomechanics of spider fangs could inspire new medical injection devices, researchers say.

"For biomedical applications, for example, the spider fang may lead to the design of new infusion techniques, new blood-bypassing instruments and many other life-saving technologies," said Benny Bar-On, a biomaterials scientist at the Max Planck Institute of Colloids and Interfaces in Germany and co-author of the study published today (May 27) in the journal Nature Communications. (Gallery: Spooky Spiders)

Spider fangs have evolved to penetrate the external skeleton of the arachnids' prey, usually insects, in order to inject venom, the researchers said. As such, the fangs have to be able to withstand significant forces without deforming or breaking.

In this study, Bar-On and his colleagues investigated the structural mechanics of the wandering spider Cupiennius salei, which is mostly found in Central America. Wandering spiders don't build a web to catch their prey; instead, they hunt around on the ground.

The researchers chose C. salei because it's easy to breed this species in large numbers year round in the laboratory. They modeled its fangs structurally in experiments and in simulations.

Unlike other biological injection needles, such as mosquito and bee stingers, the fangs of these spiders are curved. The curvature enables the arachnids to attack from different directions and hold their prey in place as they inject their venom, the researchers found.

The hollow, conical shape of the spiders' fangs gives them nearly optimal stiffness per unit volume — a measure of their resistance to deformation — making them ideally suited for piercing prey.

The fangs are a composite of protein and chitin, a carbohydrate molecule found in the shells of many insects and crustaceans, whose microscopic structure is well suited for its purpose, the results suggest.

Understanding the biomechanics of spider fangs could reveal how other sharp structures, from a scorpion's stinger to a mammoth's tusk, evolved in nature, the researchers said. Furthermore, the fangs' design might inspire scientists to develop better injection needles and other medical devices.